So a customer brought me a boat with a blown 509 in it with a 1071 blowershop blower and rootz efi being driven by a fast xfi control and a msd 6560 msd marine box. The motor had one dead cylinder, tore the engine down and had a broke intake pushrod and the lifter had jumped out. Fixed that with all new lifters pushrods and rocker arms. Ran the motor and now have 2 cylinders that aren’t firing in the cylinder. #6 and #8 they have spark outside the cylinder but it’s not the best. Replaced cap, rotor. Cleaned magnetic pickup. Swapped out the coil for another one. And still nothing. The msd is driven by the fast xfi. Could there be an underlying issue between the 2? I find it odd that it has spark outside the cylinder but won’t light it under compression. When cold you can hear it fire every now and then. Lifters were set to half a turn preload. Cranking compression is 155psi. Any help would be appreciated.

I’m sure that it happens given the heavy duty aftermarket units, but I’ve never seen a broken pushrod myself. Is the cam any good or is it wiped flat making dead holes? Was it a Bob M cam and the valvetrain beat itself to death, lol.

it had the old Johnson’s so I replaced them with the comp 854 which are the same dimensions.

cam is fine and the dead cylinders aren’t the ones that had pushrod issues.